<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        div{
            display: inline;
            background-color: red;
            width: 100px;
            height: 100px;
            border: 1px solid black;
        }
        span{
            display: block;
            background-color: red;
            width: 100px;
            height: 100px;
            border: 1px solid black;
        }

    </style>
</head>
<body>
<!--行内元素 和块级元素 没有太明显的界限
可以通过display 属性  将二者进行转换-->
<div>AAAAAA</div><div>BBBBBB</div>
<hr>
<span>CCCCCC</span>
<span>DDDDDD</span>
</body>
</html>